JPH0582968A - Multilayered printed wiring board - Google Patents

Abstract

PURPOSE:To obtain a multilayered printed wiring board provided with a through-hole the wall surface of which is not damaged by the pre-processing for plating the through hole. CONSTITUTION:In this multilayered printed wiring board which is constituted by putting an internal-layer material 1 on which a conductive circuit 2 is formed between external-layer substrates 3 respectively provided with conductive circuits 4 on their surfaces, lands 5 which are connected to the conductive circuits 2 and lands 7 which are not connected to the conductive circuits 2 are formed on both surfaces of the material 1 where a through-hole 8 is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer printed wiring board used for mounting electronic parts and electric parts. In particular, it relates to a multilayer printed wiring board having a small diameter.

[0002]

2. Description of the Related Art In recent years, electronic parts have been mounted on printed wiring boards in an even higher density. For this reason, there has been a demand for a multilayer printed wiring board in which fine circuit patterns or fine holes are accurately processed.
Japanese Unexamined Patent Publication (Kokai) No. 62-287696 discloses a fine perforating method in which about half of the plate thickness is punched from mutually opposite surfaces. Further, when the diameter of the through hole is 0.35 mm or less, the conventional ordinary through hole processing conditions should be applied more restrictively.

FIG. 3 shows a cross-sectional view of a through hole portion of a multilayer printed wiring board punched by a conventional method. In the multilayer printed wiring board, an inner layer material 1 having a conductive circuit 2 arranged on the surface and outer layer substrates 3 and 3 sandwiching the inner layer material 1 are arranged on both sides. Conductive circuits 4 and 4 are also provided on the surfaces of the outer layer substrates 3 and 3. In order to electrically connect the conductive circuit 4 of the outer layer substrate 3 and the conductive circuit 2 of the inner layer material 1, a through hole 8 penetrating each land 5, 6 and a plating layer 9 are formed on the wall surface thereof.

[0004]

When the diameter of the through hole becomes smaller, ultrasonic waves, high-pressure water washing or honing are performed as a treatment before through-hole plating for the purpose of removing resin smears and cutting debris generated by through-hole processing.
However, it may not be possible to remove them by these methods, and a method using an alkaline permanganate solution is used as a wet method for the desmear treatment. At this time, the land 5 connected to the conductive circuit 2 on the through-hole wall surface or the through-hole wall surface perforated in the portion 10 of the inner layer material having no independent land (not shown) has a resin content rate higher than that of other through hole wall surface portions. Since the amount is large, a phenomenon occurs in which the metal is scraped off by a series of desmear treatment with an alkaline permanganate solution consisting of pretreatment, smear removal, and posttreatment. Therefore, there is a problem that the connection reliability is reduced.

Therefore, it is an object of the present invention to provide a multilayer printed wiring board having a through hole wall surface which is not damaged by the pretreatment of through hole plating.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is characterized by a through hole in a multilayer printed wiring board including an inner layer material having a conductive circuit formed on the surface and an outer layer board. The multilayer printed wiring board has lands larger than the through holes on both surfaces of the inner layer material where the holes are formed. The present invention will be described below with reference to the drawings. The present invention is not limited to these examples.

[0007]

1 is a sectional view of a multilayer printed wiring board according to the present invention, and FIG. 2 is a sectional view of a multilayer laminated board before formation of through holes.

In the multilayer printed wiring board shown in FIG. 1, an inner layer material 1 having a conductive circuit 2 on its surface and outer layer substrates 3 and 3 sandwiching the inner layer material 1 are disposed on both sides. The conductive circuit 4 is also arranged on the outer surface of the outer layer substrate 3. For the purpose of conducting the conductive circuit 4 of the outer layer substrate 3 and the conductive circuit 2 on one surface of the inner layer material 1, through holes 8 penetrating the lands 5 and 6 connected to the respective conductive circuits 2 and 4 are perforated to form a plating layer. 9 is formed. Also, this through hole 8
Is also pierced by passing through an independent land 7 formed on the other surface of the inner layer material 1. The independent land 7 is a land which is formed on the same surface and is not connected to the conductive circuit 2. The shapes of these lands 5, 6, and 7 are not particularly limited, such as a quadrangle, a circle, an ellipse, and a teardrop, as long as they have a space width capable of ensuring insulation with other conductive circuits.

The multilayer laminate for the multilayer printed wiring board of the invention can be produced as follows. One or a plurality of prepregs obtained by impregnating a base material with a resin and semi-curing them are stacked, and a metal foil to be the conductive circuit 2 is laid on the outer surface of the prepreg, and the molding condition temperature is 140 to 180 ℃, pressure is 30 to 70 kg / Cm ²
The inner layer material 1 is made by primary molding in 70 to 120 minutes. In the case of this primary molding, the temperature is the glass transition point of the resin (hereinafter, T
It is particularly preferable to employ the following (described as g).

Next, the conductive circuit 2 is formed on the metal foil on the surface of the inner layer material 1 by a conventional method. When forming the conductive circuit 2, a land to be connected to the conductive circuit or an independent land not to be connected is always provided at a position where a through hole is formed when processing the multilayer laminated board into a multilayer printed wiring board.

One or a plurality of the above-mentioned prepregs are laminated on both surfaces of the inner layer material 1, and a metal foil to be the conductive circuit 4 is further laminated on both outer surfaces of the prepreg to obtain a molding temperature 140.
Secondary molding is carried out at ˜180 ° C. and pressure of 30˜70 kg / cm ² for 70˜120 minutes to make a multi-layer board having outer layer substrates 3, 3.

As a material used for making the above-mentioned multilayer laminate, epoxy resin, polyimide resin, fluororesin, PPO resin, unsaturated polyester resin and the like can be used alone or modified or mixed resins thereof. .. Moreover, it is also possible to use a resin containing an inorganic filler or an organic filler in these resins. As the base material impregnated with these resins, glass cloth, non-woven cloth and the like are usually used. In addition, organic fiber paper such as cellulose fiber paper or the like, or woven or non-woven fabric such as inorganic fiber such as quartz fiber or high heat resistant organic fiber such as polyimide resin fiber may be used alone or in combination depending on the application. Can be used.

As the metal foil provided on the surface of the inner layer material and the surface of the multi-layer laminate, a metal foil of copper, aluminum, nickel, stainless steel or the like is preferable, and a copper foil is particularly preferable in terms of good electric conductivity. .. In this case, either electrolytic copper foil or rolled copper foil may be used without any particular limitation. Alternatively, the above metal foil in which a circuit is formed on the metal foil may be used.

FIG. 2 is a cross-sectional view of a multilayer laminated board before formation of through holes, which is a multilayer printed wiring board having a through hole wall surface of the present invention. To make a multilayer printed wiring board from this multilayer laminated board, the outer layer substrate 3 is Lands connected to the respective conductive circuits 2 and 4 for the purpose of forming a predetermined conductive circuit 4 on the surface metal foil and connecting the conductive circuit 4 of the outer layer substrate 3 and the conductive circuit 2 of one surface of the inner layer material to each other. The through hole 8 indicated by a dotted line so as to connect through 5 and 6 is drilled and drilled to remove resin smears and cutting debris generated in the through hole. As the desmear treatment, for example, a method using an alkaline permanganate solution which is often used in one of wet methods can be used. In this method, conditioning with high temperature alkali or solvent,
Three steps of immersion in an alkaline potassium permanganate solution and neutralization (reduction) are sequentially performed.

Even by such a treatment, there is an independent land 7 larger than the through hole at a portion of the inner layer material 1 where the through hole 8 is drilled, and there is no land 5 larger than the through hole connected to the conductive circuit. In the above, it is possible to prevent the resin content from increasing. Therefore, it is possible to prevent the resin portion from being scraped off by the desmear treatment. Therefore, it is possible to form a uniform plating layer 9 on the through hole.

[0016]

Since the land that is connected to the conductive circuit of the inner layer material or the land that is larger than the non-connected through hole is formed on both surfaces of the inner layer material where the through hole is formed in the multilayer printed wiring board, Compared to the case where there is no large land, it is possible to prevent the wall surface of the through-hole with a high resin content from continuing continuously, so the desmear treatment prevents this resin from being scraped off, and it is possible to form a uniform plating layer on the through-hole. it can.

[0017]

In the multilayer printed wiring board of the present invention, the through-hole wall surface is not damaged by the pretreatment of through-hole plating. Therefore, the plated layer can be uniformly formed on the through hole.

[Brief description of drawings]

FIG. 1 is a sectional view showing a multilayer printed wiring board according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a multilayer laminated plate before through-hole processing according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a conventional multilayer printed wiring board.

[Explanation of symbols]

 1 inner layer material 2, 4 conductive circuit 3 outer layer substrate 5, 6, 7 land 8 through hole 9 plating layer

Claims (1)

[Claims] 1. A multilayer printed wiring board comprising an inner layer material having a conductive circuit formed on the surface and an outer layer substrate, characterized in that the inner layer material at the location where the through hole is formed has a land larger than the through hole. Multilayer printed wiring board.